/* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2005,2006,2007 INRIA

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#include "ipv4-checksum.h"

namespace ns3 {

uint16_t 

Ipv4ChecksumCalculate (uint16_t checksum, uint8_t *buffer, uint16_t size)

{

  /* see RFC 1071 to understand this code. */

  uint32_t sum = checksum;

  uint16_t *data = (uint16_t *) buffer;

  for (uint16_t i = 0; i < (size/2); i++) {

    sum += data[i];

  }

  if ((size % 2) != 0) {

    uint8_t tmpBuf[2];

    tmpBuf[0] = buffer[size-1];

    tmpBuf[1] = 0;

    data = (uint16_t *)tmpBuf;

    sum += *data;

  }

  while (sum >> 16) {

    sum = (sum & 0xffff) + (sum >> 16);

  }

  return sum;

}

uint16_t 

Ipv4ChecksumComplete (uint16_t checksum)

{

  return ~checksum;

}

}; //namespace ns3